[PATCH ath-next] wifi: ath12k: Fix the assignment of logical link index

[Roopni Devanathan <roopni.devanathan@oss.qualcomm.com>]

From: Manish Dharanenthiran <manish.dharanenthiran@oss.qualcomm.com>

Per-link logical index is assigned from the global counter,
ahsta->num_peer. This logical index is sent to firmware during peer
association. If there is a failure in creating a link station,
ath12k_mac_free_unassign_link_sta() clears the link, but does not decrement
the logical link index. This will result in a higher logical link index for
the next link station created. Also, if there is a leak in logical link
index as we assign the incremented num_peer, then the index can exceed the
maximum valid value of 15.

As an example, let's say we have a 2 GHz + 5 GHz + 6 GHz MLO setup. So the
logical link indices that they have are 0, 1 and 2, respectively. If the
5 GHz link is removed, logical link index 1 becomes available, and num_peer
is not reduced to 2 and still remains at 3. If a new 5 GHz link is added
later, it gets the index 3, instead of reusing link index 1. Also,
num_peer is increased to 4, though only 3 links are present.

To resolve these, create a bitmap, free_logical_link_idx, that tracks the
available logical link indices. When a link station is created, select the
first free logical index and when a link station is removed, mark its
logical link index as available by setting the bit.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.6-01181-QCAHKSWPL_SILICONZ-1

Signed-off-by: Manish Dharanenthiran <manish.dharanenthiran@oss.qualcomm.com>
Signed-off-by: Roopni Devanathan <roopni.devanathan@oss.qualcomm.com>
---
 drivers/net/wireless/ath/ath12k/core.h |  2 +-
 drivers/net/wireless/ath/ath12k/mac.c  | 16 ++++++++++++++--
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/ath/ath12k/core.h b/drivers/net/wireless/ath/ath12k/core.h
index 990934ec92fc..5498ff285102 100644
--- a/drivers/net/wireless/ath/ath12k/core.h
+++ b/drivers/net/wireless/ath/ath12k/core.h
@@ -522,7 +522,7 @@ struct ath12k_sta {
 	u16 links_map;
 	u8 assoc_link_id;
 	u16 ml_peer_id;
-	u8 num_peer;
+	u16 free_logical_link_idx_map;
 
 	enum ieee80211_sta_state state;
 };
diff --git a/drivers/net/wireless/ath/ath12k/mac.c b/drivers/net/wireless/ath/ath12k/mac.c
index 68431a0e128e..db1b098b67d0 100644
--- a/drivers/net/wireless/ath/ath12k/mac.c
+++ b/drivers/net/wireless/ath/ath12k/mac.c
@@ -6784,6 +6784,8 @@ static void ath12k_mac_free_unassign_link_sta(struct ath12k_hw *ah,
 		return;
 
 	ahsta->links_map &= ~BIT(link_id);
+	ahsta->free_logical_link_idx_map |= BIT(arsta->link_idx);
+
 	rcu_assign_pointer(ahsta->link[link_id], NULL);
 	synchronize_rcu();
 
@@ -7102,6 +7104,7 @@ static int ath12k_mac_assign_link_sta(struct ath12k_hw *ah,
 	struct ieee80211_sta *sta = ath12k_ahsta_to_sta(ahsta);
 	struct ieee80211_link_sta *link_sta;
 	struct ath12k_link_vif *arvif;
+	int link_idx;
 
 	lockdep_assert_wiphy(ah->hw->wiphy);
 
@@ -7120,8 +7123,16 @@ static int ath12k_mac_assign_link_sta(struct ath12k_hw *ah,
 
 	ether_addr_copy(arsta->addr, link_sta->addr);
 
-	/* logical index of the link sta in order of creation */
-	arsta->link_idx = ahsta->num_peer++;
+	if (!ahsta->free_logical_link_idx_map)
+		return -ENOSPC;
+
+	/*
+	 * Allocate a logical link index by selecting the first available bit
+	 * from the free logical index map
+	 */
+	link_idx = __ffs(ahsta->free_logical_link_idx_map);
+	ahsta->free_logical_link_idx_map &= ~BIT(link_idx);
+	arsta->link_idx = link_idx;
 
 	arsta->link_id = link_id;
 	ahsta->links_map |= BIT(arsta->link_id);
@@ -7630,6 +7641,7 @@ int ath12k_mac_op_sta_state(struct ieee80211_hw *hw,
 	if (old_state == IEEE80211_STA_NOTEXIST &&
 	    new_state == IEEE80211_STA_NONE) {
 		memset(ahsta, 0, sizeof(*ahsta));
+		ahsta->free_logical_link_idx_map = U16_MAX;
 
 		arsta = &ahsta->deflink;
 

base-commit: 62f9b9b19939138c34ce0ac1e5d4969d617ecbb6
-- 
2.43.0